A woman places flowers in commemoration of the victims of Malaysia Airlines MH17 in eastern Ukraine in front of the Malaysia embassy in Kiev on July 19. / Roman Pilipey, epa

by Jessica Durando, USA TODAY Network

by Jessica Durando, USA TODAY Network

Following the Malaysia Airlines Flight MH17 crash Thursday - which killed all 298 on board - many questions remain.

USA TODAY Network lists what we know now about the downed plane as the international community seeks answers:

What challenges remain at the crash site?

Malaysian Transport Minister Liow Tiong Lai said Saturday he is "deeply concerned" that the crash site is being tampered with. Lai said that there are "indications that vital evidence has not been preserved in place," undermining the investigation.

An international delegation visited the crash site Friday evening but was only allowed a superficial visit to see one small portion.

Ukraine and Russian-backed separatists agreed Saturday to set up a security zone around the crash site of a Malaysia Airlines jet to allow the orderly removal of the bodies.

Who was on board Flight 17?

The jetliner was carrying 298 people. The victims came from 11 countries.

The victims include 193 Dutch (including one dual Netherlands/U.S. citizen), 43 Malaysians (including 15 crew members and two infants), 27 Australians, 12 Indonesians (including one infant), 10 Britons (including one dual U.K./S. Africa citizen, four Germans, four Belgians, three Filipinos, one Canadian and one New Zealander, according to the full flight manifest released by Malaysia Airlines on Saturday.

Malaysia Airlines and foreign embassies have "made every effort to establish contact with the next-of-kin" of the dead but still are unable to "identify many more family members," the airliner said in a statement.

What kind of missile shot down the plane?

U.S. officials say it was a SA-11 surface-to-air missile that downed the Boeing 777. It is also known as a Buk, which was first built by the Soviet Union and is capable of shooting down jets traveling up to 70,000 feet.

Who took down the jetliner?

The latest U.S. intelligence assessment suggests that more than one missile system was provided to the separatists by the Russians in the last week or so, a U.S. official said Saturday, according to media reports. The official said it's not entirely clear if the separatists just received the missile systems or if they had them for a short time and only in recent days were trained or able to operate them.

The Pentagon said Friday it is unlikely that pro-Russian separatists in east Ukraine could obtain or operate the sophisticated missile system allegedly used to shoot down the Malaysia Airlines plane without Russian help.

The Pentagon says there is strong evidence the missile, a SA-11, was fired by Russian-backed separatists since the missile was fired from an area controlled by rebels.

The Obama administration said preliminary evidence suggests the aircraft was hit by a surface-to-air missile. Ukraine's government says the jetliner was shot down by a Russian aircraft.

Where was the airliner headed?

The Malaysian airliner was en route from Amsterdam to Kuala Lumpur with 283 passengers and 15 crew members when it crashed into rebel-held territory in eastern Ukraine.